public static TreeNode GetParentNode(TreeNode node, int data)
{
if (node != null)
{
if (node.Data == data)
{
return(node);
}
if (node.Left != null && node.Left.Data == data)
{
return(node);
}
if (node.Right != null && node.Right.Data == data)
{
return(node);
}
var leftSubtree = TreeUtilities.GetParentNode(node.Left, data);
var rightSubtree = TreeUtilities.GetParentNode(node.Right, data);
return(leftSubtree ?? rightSubtree);
}
return(null);
}
public void Delete(int data)
{
var parent = TreeUtilities.GetParentNode(this.Root, data);
if (parent == null)
{
parent = this.Root;
}
if (parent != null)
{
bool isRoot;
bool deleted = parent.DeleteLeaf(data, out isRoot);
if (deleted && isRoot)
{
this.Root = null;
}
if (!deleted)
{
deleted = parent.DeleteWithOneChild(data);
if (!deleted)
{
deleted = parent.DeleteWithTwoChildren(data);
if (!deleted)
{
throw new InvalidOperationException(
"Cannot remove node for value: " + data);
}
}
}
}
}
public bool DeleteWithTwoChildren(int data)
{
bool isRoot;
if (this.Data == data)
{
if (this.Left != null && this.Right != null)
{
int smallestChildValue = FindSmallestValue(this.Right);
var smallestValueNodeToRemoveParent =
TreeUtilities.GetParentNode(this.Right, smallestChildValue);
bool isDeleted = smallestValueNodeToRemoveParent.DeleteLeaf(smallestChildValue, out isRoot);
if (isDeleted && isRoot)
{
this.Right = null;
}
if (!isDeleted)
{
isDeleted = smallestValueNodeToRemoveParent.DeleteWithOneChild(smallestChildValue);
if (!isDeleted)
{
return(false);
}
}
this.Data = smallestChildValue;
return(true);
}
}
if (this.Left != null && this.Left.Data == data)
{
if (this.Left.Left != null && this.Left.Right != null)
{
int smallestChildValue = FindSmallestValue(this.Left.Right);
var smallestValueNodeToRemoveParent =
TreeUtilities.GetParentNode(this.Left, smallestChildValue);
bool isDeleted = smallestValueNodeToRemoveParent.DeleteLeaf(smallestChildValue, out isRoot);
if (isDeleted && isRoot)
{
this.Left = null;
}
if (!isDeleted)
{
isDeleted = smallestValueNodeToRemoveParent.DeleteWithOneChild(smallestChildValue);
if (!isDeleted)
{
return(false);
}
}
this.Left.Data = smallestChildValue;
return(true);
}
}
if (this.Right != null && this.Right.Data == data)
{
if (this.Right.Left != null && this.Right.Right != null)
{
int smallestChildValue = FindSmallestValue(this.Right.Right);
var smallestValueNodeToRemoveParent =
TreeUtilities.GetParentNode(this.Right, smallestChildValue);
bool isDeleted = smallestValueNodeToRemoveParent.DeleteLeaf(smallestChildValue, out isRoot);
if (!isDeleted)
{
isDeleted = smallestValueNodeToRemoveParent.DeleteWithOneChild(smallestChildValue);
if (!isDeleted)
{
return(false);
}
}
this.Right.Data = smallestChildValue;
return(true);
}
}
return(false);
}